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Yum, Lego… Human babies born to move hands to mouth

DON’T blame the baby for trying to eat that Lego piece. Humans may have a brain circuit dedicated to grabbing stuff and putting it in our mouths, and it probably develops in the womb.

Researchers and parents alike have long known that babies stick all manner of things in their mouths from very early on. Some fetuses even suck their thumbs.

As putting something in the mouth seems advanced compared to the other, limited actions of newborns, Angela Sirigu of the Institute of Cognitive Sciences in Bron, France, and colleagues wondered whether the behaviour is encoded in the brain from birth.

To investigate, they studied 26 people of different ages while they were undergoing brain surgery. The researchers found that they were able to make nine of the unconscious patients bring their hands up and open their mouths, just by stimulating a brain region linked to those actions in other primates (PNAS, DOI&colon; 10.1073/pnas.1321909111).

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Because this behaviour is encoded in the same region as in other primates, it may be there from birth or earlier, the researchers say. If it was learned, you would expect it to involve multiple brain areas, and those could vary between individuals.

Newborn kangaroos are able to climb into their mother’s pouch and baby wildebeests can run away from lions, but our babies appear helpless and have to learn most complex actions. The new work suggests the way our brain develops is more similar to brain development in other animals than previously thought.

This article appeared in print under the headline “A baby’s urge to chew on Lego is automatic, not learned”